Each launcher has its respective store, these can be viewed at https://steam.elitedangerous.com and https://store.elitedangerous.com
Steam or rather Valve deserve praise for what they've done but I think it's a bit hyperbolic to say the survival of PC gaming rests entirely on their shoulders.
I wasn't aware of the steam store, that means a few of my earlier comments were false, sorry about that. Still, I maintain that both Valve and Frontier are both successful multi-billion dollar companies, and Frontier wouldn't enter into an agreement, or allow their players options (eg. to buy from steam) that wouldn't benefit them in the long run. I understand that they would prefer if we bought directly from them, but they have considered their options and decided to give steam keys to all previous customers. I'm sure people buying from steam is not going to send the company into financial ruin, quite the opposite, I think Frontier is showing they respect their customers enough to give them options. This definitely makes me more interested in buying more products from them in the future.